Septic tanks are of course well known in the art. Septic tanks intended for domestic use are generally square or rectangular in construction and usually have two chambers or compartments allowing for digestion, settling and holding of sewage prior to effluent discharge, generally to a leach field. These known systems are disadvantageous in a number of ways. The rectangular configuration is generally weak when buried beneath the soil because of both hydrostatic pressures within the tank and external pressures from soil compaction and movement. Because of these weaknesses and because of the shape, rectangular septic tanks are more costly to build, requiring more man hours to construct and requiring thicker cement and extra steel reinforcing bar over the design described herein.
Although cylindrically configured tanks have been used, these systems have generally been employed in large scale sewage-treatment operations. They tend to be complex with many subchambers and partitions designed for a multi-treatment process. See, for example, U.S. Pat. No. 4,882,046 to Waite. These systems generally incorporate mechanical parts or complicated duct work which require period maintenance. Such maintenance requirements make such systems unsuitable for domestic use because local health authorities generally require that residential septic tanks be essentially maintenance-free, apart from periodic sludge removal by pumping.
There exists therefore a need for a cylindrically configured, inexpensive, easy to install sewage treatment tank for domestic use.
It is therefore an object of the present invention to provide a domestic sewage treatment system that is simple in design and that requires no maintenance once installed, other than periodic pumping.
It is another object of the present invention to provide a domestic sewage treatment system that can readily withstand hydrostatic and ground forces without the need for extra materials and labor.
It is a further object of the present invention to provide a sewage treatment system that is inexpensive and easy to manufacture and install.